Hello World - Assembly Language (ARM 920T)

This is a "Hello World" program written in pure assembly language on Linux/ARM 920T platform.

  1 #
  2 # Makefile for Hello World on Linux/ARM 920T platform
  3 #
  4 all:
  5     arm-linux-as hello.s -o hello.o
  6     arm-linux-ld hello.o -o hello
  7 
  8 clean:
  9     rm -rf hello hello.o
 
  1 
  2 .text
  3 .global _start
  4 _start:
  5 
  6     mov r0,     #1
  7     adr r1,     msg
  8     mov r2,     #14
  9     swi 0x00900004
 10 
 11     mov r0, #0
 12     swi 0x00900001
 13 
 14 msg: .asciz "Hello World\n"

Result...

$ uname -a
Linux ARM 2.6.11.1armzone_linux2.6 #6 Fri Dec 12 12:12:23 CST 2008 armv4tl unknown
$ ./hello
$
Hello World
$

Of Linux on ARM 920T CPU...

The Linux kernel entry, from user mode application into kernel mode, is triggled by swi (0x00900001 or index) instrusion.

The system call number is got from the low byte of swi parameter (swi 0x009000XX).

The system call parameter is placed in the sequence of r0, r1, r2...

In the example of the WRITE() system call

ssize_t write (int __fd, __const void *__buf, size_t __n);
 The system call index (g1) is 0x04 (swi 0x00900004)
 __fd  is r0
 __buf is r1
 __n   is r2